Abstract

Seed germination of two species of the Himalayan rhubarb (Rheum acuminatum andRheum australe) growing in high altitudes was simulated by different fluctuating temperatures. The germination experiments in different temperature regimes (15/5, 20/5, and 25/10°C) of fluctuating light regime of 12 h day and 12 h night, and same temperature regimes of constant darkness showed that both species germinated better in light than in complete darkness. An overall percentage of germination was higher for R. acuminatumthan for R. australe both in light and complete darkness. The optimum temperature for R. acuminatum was 15/5°C light (around 87.08%) and lowest was 15/5°C dark (9.62%). Similarly, R. australe germinated well at 20/5°C light (61.39%) and least at 15/5°C dark (4.71%). When testing effects of different factors on the germination, it was found that there was a positive effect of seed mass and also interaction of light and temperature. Looking at patterns of germination, smaller seeds of R. acuminatum germinated faster than bigger seeds of R. australe in all temperature regimes except 25/10°C dark conditions. Seeds of both species will germinate better if shifted to lower altitudes where temperatures are higher than at their actual habitats. Since both species lack in seed bank, it is recommended that seed sowing should be carried out in spring rather than before winter for better germination.

Key words: Himalayan region, rhubarb, Rheum acuminatum, Rheum australe, seed germination.